Direct constraint on the distance of Gamma2 Velorum from AMBER/VLTI observations.

F. Millour (1, 2) , R. G. Petrov (2) , O. Chesneau (3, 4) , D. Bonneau (3) , L. Dessart (5) , Clémentine Béchet (6) , Isabelle Tallon-Bosc (6) , Michel Tallon (6) , Éric Thiébaut (6) , F. Vakili (2) , F. Malbet (1) , D. Mourard (3, 4) , G. Zins (1) , A. Roussel (3, 4) , S. Robbe-Dubois (2) , P. Puget (1) , K. Perraut (1) , F. Lisi (7) , E. Le Coarer (1) , S. Lagarde (3, 4) , P. Kern (1) , L. Glück (1) , G. Duvert (1) , A. Chelli (1) , Y. Bresson (3, 4) , U. Beckmann (8) , P. Antonelli (4) , G. Weigelt (8) , N. Ventura (1) , M. Vannier (2, 9) , J.-C. Valtier (4) , L. Testi (7) , E. Tatulli (1) , D. Tasso (4) , P. Stefanini (7) , P. Stee (4) , W. Solscheid (8) , D. Schertl (8) , P. Salinari (7) , M. Sacchettini (1) , A. Richichi (9) , François Reynaud (10) , S. Rebattu (4) , Y. Rabbia (4) , T. Preibisch (8) , C. Perrier (1) , F. Pacini (7) , K. Ohnaka (8) , E. Nussbaum (8) , D. Mouillet (1, 11) , J.-L. Monin (1) , P. Mège (1) , P. Mathias (4) , G. Martinot-Lagarde (4, 12) , G. Mars (4) , A. Marconi (7) , Y. Magnard (1) , B. Lopez (4) , D. Le Contel (4) , J.-M. Le Contel (4) , S. Kraus (8) , D. Kamm (4) , K.-H. Hofmann (8) , O. Hernandez Utrera (1) , M. Heininger (8) , M. Heiden (8) , C. Gil (1) , E. Giani (7) , A. Glentzlin (4) , S. Gennari (7) , A. Gallardo (1) , D. Didier Fraix-Burnet (1) , Renaud Foy (6) , E. Fossat (2) , T. Forveille (1, 13) , D. Ferruzzi (7) , P. Feautrier (1) , M. Dugué (3, 4) , T. Driebe (8) , A. Domiciano de Souza (2, 8) , A. Delboulbé (1) , C. Connot (8) , J. Colin (4, 14) , J.-M. Clausse (4) , F. Cassaing (15) , S. Busoni (7) , S. Bonhomme (1, 4) , T. Blöcker (8) , J. Behrend (8) , C. Baffa (7) , E. Aristidi (2) , B. Arezki (1) , K. Agabi (2) , B. Acke (1) , M. Accardo (7) , M. Kiekebusch (9) , F. Rantakyrö (9) , Markus Schoeller (9)

1 LAOG - Laboratoire d'Astrophysique de Grenoble
2 LUAN - Laboratoire Universitaire d'Astrophysique de Nice
3 CASSIOPEE - Laboratoire de Cosmologie, Astrophysique Stellaire & Solaire, de Planétologie et de Mécanique des Fluides
4 LG - Laboratoire Gemini
5 STEWARD OBSERVATORY - Steward Observatory
6 CRAL - Centre de Recherche Astrophysique de Lyon
7 OAA - INAF - Osservatorio Astrofisico di Arcetri
8 MPIFR - Max-Planck-Institut für Radioastronomie
9 ESO - European Southern Observatory
10 PHOTONIQUE
11 LATT - Laboratoire Astrophysique de Toulouse-Tarbes
12 DTI - Division technique INSU/SDU
13 OSUG - Observatoire des Sciences de l'Univers de Grenoble
14 OCA - Observatoire de la Côte d'Azur
15 ONERA - The French Aerospace Lab [Châtillon]

In this work, we present the first AMBER observations, of the Wolf-Rayet and O (WR+O) star binary system y² Velorum. The AMBER instrument was used with the telescopes UT2, UT3, and UT4 on baselines ranging from 46m to 85m. It delivered spectrally dispersed visibilities, as well as differential and closure phases, with a resolution R = 1500 in the spectral band 1.95-2.17 micron. We interpret these data in the context of a binary system with unresolved components, neglecting in a first approximation the wind-wind collision zone flux contribution. We show that the AMBER observables result primarily from the contribution of the individual components of the WR+O binary system. We discuss several interpretations of the residuals, and speculate on the detection of an additional continuum component, originating from the free-free emission associated with the wind-wind collision zone (WWCZ), and contributing at most to the observed K-band flux at the 5% level. The expected absolute separation and position angle at the time of observations were 5.1±0.9mas and 66±15° respectively. However, we infer a separation of 3.62+0.11-0.30 mas and a position angle of 73+9-11°. Our analysis thus implies that the binary system lies at a distance of 368+38-13 pc, in agreement with recent spectrophotometric estimates, but significantly larger than the Hipparcos value of 258+41-31 pc.

Domaines: Cosmologie et astrophysique extra-galactique [astro-ph.CO]; Cosmologie et astrophysique extra-galactique [astro-ph.CO]; Astrophysique [astro-ph]

F. Millour, R. G. Petrov, O. Chesneau, D. Bonneau, L. Dessart, et al.. Direct constraint on the distance of Gamma2 Velorum from AMBER/VLTI observations.. Astronomy and Astrophysics - A&A, 2007, pp.107-118. ⟨10.1051/0004-6361:20065408⟩. ⟨hal-00110486⟩